diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
index cf76fc29d4..0b79566758 100644
--- a/src/include/access/tableam.h
+++ b/src/include/access/tableam.h
@@ -631,8 +631,8 @@ typedef struct TableAmRoutine
 									   const RelFileLocator *newrlocator);
 
 	/* See table_relation_copy_for_cluster() */
-	void		(*relation_copy_for_cluster) (Relation NewTable,
-											  Relation OldTable,
+	void		(*relation_copy_for_cluster) (Relation OldTable,
+											  Relation NewTable,
 											  Relation OldIndex,
 											  bool use_sort,
 											  TransactionId OldestXmin,